Mechanism of ammonium sulfate regulation effect on microstructure of Y2O3 nanopowders via urea precipitation method

Abstract

In the preparation of transparent ceramics and ultrafine oxide nanopowders, ammonium sulfate ((NH4)2SO4) has been widely used as the control agent. However, the mechanism of its regulation effect has not been well studied. In the present work, precursors of yttria (Y2O3) nanopowders with controlled morphology were synthesized via a urea precipitation method using ammonium sulfate as the additive. The effect of (NH4)2SO4 is discussed throughout the preparation process. Two opposite morphology transformation modes were noticed for the precursor samples made with and without (NH4)2SO4 during the calcination process. Flocculent precursors and flowers assembled by the plate-shaped particles were obtained in the systems without and with (NH4)2SO4. By calcination, the aggregated 200–400 nm particles with massive defects and 100 nm particles with homogeneous crystalline structure were obtained, respectively. The mechanism of (NH4)2SO4 as a regulator that could mediate the nucleation and growth of the precursors as well as its decomposition behavior is verified.